In recent years, with the purpose of saving energy and suppressing the emission of carbon dioxide, performing an idling stop by automatically stopping the engine without idling when the automobile has stopped, has been considered, and some idling-stop vehicles having this kind of idling-stop function are actually being used. In the case of this kind of idling-stop vehicle, when the automobile stops, the vehicle-speed sensor detects a zero-speed signal, and the engine is automatically stopped (without operating the ignition switch) based on the zero-speed signal. On the other hand, when starting the automobile moving again, based on a signal from a clutch sensor (in the case of a manual-transmission automobile) that detects movement of the clutch pedal, or an accelerator sensor or brake sensor (in the case of an automatic-transmission automobile) that detects when the accelerator pedal or brake pedal moves, the automobile engine is automatically started again (without operating the ignition switch). With this kind of idling-stop automobile, it is possible to save energy and to suppress emission of carbon dioxide during this idling stop of the engine.
In the case of this kind of idling-stop automobile, it is necessary to be able to start the engine more quickly than in the case of a normal automobile. Therefore, it is difficult to employ the typically used construction in which a pinion that is fastened to the drive shaft of the start motor meshes, only during starting, with a large gear that is fastened to a flywheel. Taking this into consideration, as shown in FIG. 55, construction has been proposed in which an endless belt 7 runs around a follower pulley 3 that is fastened to the end of the crankshaft 2 of the engine 1, and to the drive-pulley apparatus that is fastened to the end of the rotation-drive shaft 5 of the starter motor 4. When employing this kind of construction in the starting apparatus of an engine, a drive-pulley apparatus 6 having a built-in one-way clutch is used, so that power is transmitted from the rotation-drive shaft 5 to the endless belt 7, however, that power is not transmitted from this endless belt 7 to the rotation-drive shaft 5. In an actual engine, there are various auxiliary drive apparatuses installed such as an alternator and water pump, however, since this invention is not directly related to these drive apparatuses, they are omitted in the drawings.
With the starting apparatus for an engine having the construction described above, when starting engine, electric power flows to the starter motor 4 to rotate and drive the drive-pulley apparatus 6, which then rotates and drives the crankshaft 2 by way of the endless belt 7 and follower pulley 3. At this time, the one-way clutch that is built into the drive-pulley apparatus 6 is engaged (becomes locked), and transmits power from the rotation-drive shaft 5 to the endless belt 7. As a result, after the engine has started, the connection with the one-way clutch is disconnected (becomes the overrun state), and the rotation-drive shaft 5 of the starter motor 4 does not rotate, even though the endless belt 7 is running due to the rotation of the crankshaft 2. Therefore, this starter motor 4 is not a resistance against the operation of the engine 1, and the durability of this starter motor 4 is not damaged.
As disclosed in patent document 1 and patent document 2, using a roller clutch as the one-way clutch in a pulley apparatus with built-in one-way clutch that is installed in the drive-pulley apparatus 6 of this kind of engine starting apparatus has been proposed. With construction using a roller clutch, it is possible to reduce vibration, noise and friction that occur when not connected better than when using a ratchet mechanism. Also, it is possible to reduce the internal friction that occurs when not connected better than when using a sprag-type cam clutch. The following patent documents are given as the prior art of the present application.
Patent Document 1
Japanese Patent Publication No. Tokukai Hei 11-63170
Patent Document 2
Japanese Patent Publication No. Tokuko Hei 7-72585
Patent Document 3
Japanese Patent Publication No. Tokukai 2002-174270
Patent Document 4
Japanese Patent Publication No. Tokukai Hei 9-196090
Of the patent documents listed above, the pulley apparatus with built-in one-way clutch disclosed in patent documents 1 and 2 is intended to be located on the end of the rotating shaft of the alternator which is an engine auxiliary apparatus, and thus the state of use differs greatly from that of the starting apparatus of an engine. Therefore, even when this pulley apparatus with built-in one-way clutch is mounted as is on the end of the rotation-drive shaft of a starter motor, it is not possible to obtain sufficient durability. In other words, one reason for using a pulley apparatus with built-in one-way clutch for the rotating shaft of an alternator is to make the direction of the friction acting between the inner peripheral surface of the belt and the outer peripheral surface of the pulley constant, even though there are small changes in the rpm of the engine, in order to maintain the durability of the belt. Moreover, another reason is to increase the generating efficiency by keeping the rotor of the alternator rotating due to its inertia when the rpm of the engine drops.
Therefore, a pulley apparatus with built-in one-way clutch for an alternator basically operates in the locked state, and the amount of time that it operates in the overrun state is very short when compared with the overall time of operation. Also, the amount of continuous time in the overrun state is extremely short. Taking this into consideration, in order for a roller clutch installed in a pulley apparatus with built-in one-way clutch for an alternator to securely achieve the locked condition when the engine is operating, well-known construction as shown in FIG. 56 and as disclosed in patent documents 1 and 2 is used.
In a first example of a roller clutch 8 using the conventional construction shown in FIG. 56, an inner race 9 and outer race 10 are placed such that they are concentric with each other, and there are a retainer 11, a plurality of rollers 12 and a plurality of springs 13, 13 between the outer peripheral surface of the inner race 9 and the inner peripheral surface of the outer race 10. The outer peripheral surface of the inner race 9 is a cam surface having a plurality of concave sections 14 called ramp sections, and the inner peripheral surface of the outer race 10 is a simple cylindrical surface. The convex sections 15 formed around the inner peripheral edge portion of the retainer 11 is fitted with the aforementioned concave sections 14 to prevent the rotation of retainer 11 relative to the inner race 9. In other words, the retainer 11 and inner race 9 are such that they rotate in synchronization. Also, the springs 13 push the rollers 12 in the same circumferential direction toward the shallow side of the concave sections 14.
In the case of this kind of roller clutch 8, when there is a tendency for the inner race 9 to rotate relative to the outer race 10 in the clockwise direction of FIG. 56, the rollers 12 bite into (fit into) the space between the outer peripheral surface of the inner race 9 and the inner peripheral surface of the outer race 10, and rotation force is transmitted between the inner race 9 and the outer race 10. On the other hand, when there is a tendency for the inner race 9 to rotate relative to the outer race 10 in the counterclockwise direction of FIG. 56, the rollers 12 are moved against the elastic force of the springs 13 to the deep sections of the concave sections 14, and there is decrease in the surface pressure at the points of contact between the rolling contact surfaces of the rollers 12 and the inner peripheral surface of the outer race 10, and the rotation force stops being transmitted between the inner race 9 and the outer race 10.
However, even when rotation force is not transmitted between the inner race 9 and outer race 10 in this way, rubbing at the points of contact between the rolling contact surfaces of the rollers 12 and the inner peripheral surface of the outer race 10 is unavoidable. Therefore, when the overrun state continues for a long time, friction heat that cannot be neglected occurs at the points of contact, causing the temperature inside the roller clutch 8 to rise, and making it easy for the grease inside this roller clutch to degrade. Furthermore, the temperature of the support bearing adjacent to this roller clutch 8 also rises, making it easy for the rubber or synthetic resin seal plate in this support bearing to degrade. In the case of a pulley apparatus with a built-in one-way clutch for an alternator, since operation is mainly in the locked state as described above, and the amount of time of operation on the overrun state is short, it is difficult for the rise in temperature due to the friction heat described above to become a problem.
On the other hand, in the case of the one-way clutch that is installed in a drive-pulley apparatus 6 for an idling-stop vehicle described above and as shown in FIG. 55, the amount of time that the clutch is in the locked state is only a short time when the engine starts, and after the engine starts, the clutch is in the overrun state as long as the engine is running. Therefore, it is difficult to maintain sufficient durability even when the roller clutch 8 as shown in FIG. 56 is installed in the engine starting apparatus for an idling-stop vehicle.
Taking this problem into consideration, the rotation-transmission apparatus with built-in roller clutch for starting an engine of this invention is made to make it possible to sufficiently secure durability.